An in vitro experiment indicated that vitamin D up-regulated SIRT-1 and reverted the SIRT-1 down-regulation induced by H2O2 in human endothelial cells.21 Moreover, vitamin D increased the expression and activity of SIRT-1 in 3T3-L1 adipocytes.22 In line with these findings, Chang and Kim38 study described that vitamin D deficiency significantly decreased SIRT-1 in obese rats fed with a vitamin D-insufficient diet. This evidence concerns the gene SIRT1 and vitamin D deficiency.